1. Field of the Invention
This invention relates generally to solar water heaters and, more specifically, to a control and protection system for a solar water heater, which optimizes energy collection by varying the circulating pump speed in proportion to the available temperature differential, provides freeze-up protection for the collector panel, and prevents an overheating of the reservoir tank.
2. Description of the Prior Art
In the past, the rising cost of energy has fostered the popularity of various direct conversion solar energy devices. Among the most popular of such devices was the domestic hot water heating system, wherein exposed collector panels absorbed radiant energy and transferred that energy to water or other working fluid to ultimately provide hot water at a temperature compatible with domsetic use. Most typically, the circulating fluid was simply water intended for use, minimizing system expense.
In such a circulating water system, however, several problems were presented. Among these problems was the possibility of freeze-up of the circulating fluid in the collector panel during periods of low ambient temperature, which resulted in the destruction of the panel itself. Although various attempts were made to solve the freeze-up problem, the solutions of the prior art left yet another problem, in that those devices required that the system power source remain operational to drain or otherwise protect the collector panel. Thus, where low temperatures were preceded by a power loss, the collector panel was substantially unprotected against freeze-up.
A need existed for a control and protection system for a solar hot water heater apparatus which could protect the collector panel against freeze-up even after line power had failed.